1. Field of the Invention
The present invention relates in general to a data converting apparatus for converting outline data representative of an outline of a character such as a letter and a symbol, into corresponding dot data representative of the character, and more particularly to improvements in the processing of ornamental end data representative of an ornamental end portion of an ornamented stroke of the character.
2. Discussion of the Prior Art
Characters such as letters and symbols represented by character data are printed, displayed or otherwise reproduced according to the character data suitably processed by a computer. Commonly, the character data takes the form of dot data indicating whether a dot should be formed in each of picture elements which are the smallest part of picture image and determine the resolution of the reproduced image. If a batch of dot data representative of all the characters available for reproduction is prepared and stored in a character memory, the memory should have an extremely large capacity. It is therefore desirable to store a batch of outline data representative of the outlines of the characters, and convert the outline data into the corresponding dot data by suitable data converting means, when the characters are printed, displayed or otherwise reproduced, as disclosed in Japanese Patent Publication No. 53-41017.
In converting the character outline data into the corresponding dot data, a coordinated pixel screen is used. The pixel screen has an X-Y coordinate system in which the picture elements are defined by a plurality of pixel lines parallel to the X axis, and a plurality of pixel lines parallel to the Y axis perpendicular to the X axis. Each stroke of a character is constituted by the picture elements which lie in the outline of the stroke so as to meet a predetermined requirement, when the outline of the character is superimposed on the coordinated pixel screen. The dot data of the character corresponding to the outline data is prepared such that the logical values of the bits corresponding to the picture elements within the outline of the strokes of the character indicate the presence of dots which form the strokes. The outline data is prepared based on the outlines of the characters of a given typestyle, which are designed by a typeface designer. The characters are constituted by main strokes and ornamental strokes which are usually called serifs, or by main strokes only. Some strokes of the characters may be ornamented at one end or both ends of the stroke, by suitable ornaments having a semicircular, triangular or other shape, usually called serifs. Occasionally, the serifs themselves are regarded as ornaments.
Where characters are reproduced according to dot data to which the character outline data is converted by a data converting apparatus which uses a coordinated pixel screen as discussed above, the number and positions of the picture elements which lie within the outline of a stroke of a character so as to satisfy the predetermined requirement may vary, depending upon the position at which the character is printed. Further, the number and positions of the picture elements which lie in a given area within the outline of one stroke of a character may differ from those of the picture elements which lie in the similar area within the outline of another stroke of the same character, depending upon the positions of the strokes. When the number of the picture elements constituting a character is relatively small, the configuration of an ornament or an ornamental end portion of one stroke may differ from that of an ornamental end portion of another stroke, even if these two strokes have the same width. Further, the configurations of the end portions of the strokes tend to be unpleasant. The number of the picture elements constituting a character is relatively small when the character is reproduced in a relatively small size where the characters can be reproduced in different sizes. Where a stroke of a character is ornamented at its end or ends, the number of the picture elements which form the ornamental end portion of that ornamented stroke tends to be comparatively small, if the apparatus reproducing the characters has relatively low image reproduction resolution (relatively small number of picture elements per unit area). In this case, the configurations of the ornamental end portions of different strokes of the same character may remarkably differ from each other, depending upon the positions at which the strokes are reproduced, whereby the ornamental end portions of the strokes are irregularly shaped and look offensive.
The above problem is also encountered where the outline data suitable for use on an apparatus having relatively high image reproduction resolution is utilized by an apparatus which has relatively low image reproduction resolution. In this case, the ornamental end portions of the strokes cannot be reproduced as defined by the outline data.